In the process of continuously casting metal strips, such as wide ribbons, it is common practice to use a nozzle and to dispense molten metal from an elongated slot in that nozzle. The molten metal dispensed from the elongated slot is deposited or discharged onto a relatively moving chill surface positioned intimately below or adjacent the elongated slot. The molten metal solidifies soon after contact with the chill surface. Past developments in the casting of amorphous metal strips are reviewed in U.S. Pat. No. 4,142,571. Other and older methods of continuous casting are known and shown, for example, in U.S. Pat. Nos. 2,564,723 and 2,978,761.
A conventional slot nozzle for depositing molten metal in a continuous casting operation would include a body formed of a generally rectangular piece of ceramic material. The typical nozzle has a relatively large opening on one side of the body which spans virtually the entire length of nozzle. This opening extends into a hollow interior space with the nozzle, which hollow space has a converging cross sectional configuration that terminates in a relatively narrow slot. The relatively narrow slot also spans virtually the entire length of the nozzle. Molten metal enters the nozzle through the relatively large opening into the hollow interior space and is discharged through the relatively narrow slot. A typical nozzle of this type is disclosed in U.S. Pat. No. 2,128,941 and specifically illustrated in FIG. 4 thereof.
The molten metal discharged from the relatively narrow slot of the typical prior art nozzle may be deposited onto a moving substrate positioned intimately subjacent the nozzle slot. However, when the molten metal is under pressure, it may even be discharged in any direction as, for example, in U.S. Pat. No. 2,790,216 wherein molten metal is discharged upwardly into the nip of a pair of counter rotating chilled rollers.
As depicted in the FIG. 4 illustration of the aforementioned U.S. Pat. No. 2,128,941 which shows a nozzle suspended by adjustable screws secured only to the longitudinal ends of the nozzle, it is common to support the nozzle only at its end portions.
When the metal strip being manufactured has a high aspect ratio, or width to thickness ratio, the dispensing slot of the nozzle must necessarily be correspondingly long and narrow. As nozzle slots become increasingly longer to dispense increasingly wider strips or ribbon, for example, the edges of the nozzle slot have a tendency to flex along the nozzless length.
The problem of nozzle slot flexing is accentuated when only the ends of the nozzle are supported. Such flexing of the edges of the nozzle slot may alter the slot dimensions and render the slot dimensionally unstable. This may cause deleterious variations in the thickness of the cast ribbon, or even voids in the ribbon, thus destroying its integrity. The ribbon must then be discarded resulting in substantial waste, and thus extra expense. In an extreme case, the nozzle may even break at its midsection under the resulting bending stresses. The hot molten metal is suddenly released, creating an expensive shut-down and clean-up requirement. In addition, this catastrophic failure may cause serious injury to operating personnel.
The nozzle is generally mounted in a mating ceramic crucible bottom or other mounting means. These structural elements are subject to the same bending stresses as the nozzles during use. Consequently, the mounting means (such as a plate) or crucible may flex near the mid-point of its span, aggravating the dimensional instability of the nozzle slot.
As indicated above, a nozzle is generally affixed to a mounting plate or crucible bottom from which the nozzle is supplied molten metal. The method of mounting the nozzle to the crucible bottom or mounting plate does, to some extent, influence the geometry of nozzle configurations. The upper edge of the nozzle generally has a substantially planar portion for engagement with and securement to a mating planar portion on the crucible bottom or mounting plate. The apparent geometrical limitations of prior art nozzles has precluded many otherwise available inexpensive manufacturing techniques and resulted in nozzles that are relative expensive to manufacture.